Inverter Transconductance Tuning via Dynamic Reference Voltage

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Electronic inverters with MOS transistors face challenges in maintaining constant transconductance and reducing phase noise variation across temperature and process corners, leading to increased power consumption due to the need for high reference voltages to compensate for varying transit frequencies.

Innovation Solution

A circuit with a current source and transistors that adjust the reference voltage based on temperature variations to maintain constant transconductance, using proportional-to-absolute-temperature (PTAT) circuits to provide a current that compensates for mobility and threshold voltage changes, thereby reducing phase noise and power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If high reference voltage is applied to compensate for varying transit frequencies, then transit frequency stability is improved, but power consumption increases

Engineering Contradiction:

Improvetransit frequency stabilityVSAvoidpower consumption

Core Design Contradiction:

Stability of the object's compositionVSUse of energy by moving object

Solution Approach 1:

The reference voltage is made dynamic rather than static. The circuit automatically adjusts the reference voltage based on temperature and process conditions to maintain constant transconductance. This dynamic adjustment allows the system to use higher voltage only when necessary (at high temperatures or slow process corners) and lower voltage when conditions permit, thereby maintaining frequency stability while reducing average power consumption

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the reference voltage parameter based on operating conditions. By monitoring temperature and process variations, the circuit modifies the reference voltage to compensate for transistor parameter drift, ensuring constant transconductance and transit frequency without continuously operating at maximum voltage, thus resolving the contradiction between stability and power consumption

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If reference voltage is increased to maintain constant transconductance across temperature variations, then transconductance stability is improved, but phase noise increases

Engineering Contradiction:

Improvetransconductance stabilityVSAvoidphase noise

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The reference voltage is dynamically adjusted based on temperature conditions. At lower temperatures where transistors naturally operate faster, the reference voltage is reduced, avoiding unnecessary high-voltage operation that would generate phase noise. At higher temperatures, the voltage is increased only enough to maintain constant transconductance, minimizing phase noise while ensuring stability

Inventive Principle:

Principle #15Dynamics

3Speed

If high current is used to ensure sufficient transition speed at all temperatures, then transition speed is improved, but power consumption increases

Engineering Contradiction:

Improvetransition speedVSAvoidpower consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The bias current is made dynamic by adjusting the reference voltage based on temperature and process conditions. The circuit ensures sufficient transition speed by providing higher current only when necessary (at high temperatures or slow process corners) and reducing current when transistors naturally operate faster, thereby maintaining adequate transition speed across all conditions while minimizing average power consumption

Inventive Principle:

Principle #15Dynamics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution achieves reduced phase noise and power consumption by maintaining constant transconductance and transit frequencies across temperature and process variations, with phase noise reduced to less than 1 dB and power consumption minimized by only increasing current when necessary.

Implementation Method 1

An output current of the current source varies with temperature at a first rate that corresponds to a second rate at which a transconductance value of the first transistor and the second transistor varies with temperature

Methodology Applied

Scientific EffectProportional-to-absolute-temperature (PTAT) effect:

Data Source

PatentUS8963621B2Methods and apparatus for tuning a current source and selecting a reference voltage to maintain a transconductance and transition frequencies of transistors of an inverter

Publication Date: 2015.02.24 MARVELL ASIA PTE LTD

AI summary

A circuit including a current source, an inverter, and a device. The current source is configured to receive a first reference voltage and supply an output current. The inverter has a transconductance. The inverter includes a first transistor having a source and a drain and a second transistor having a source. The source of the first transistor is connected to the current source. The source of the first transistor is configured to receive a portion of the output current. The source of the second transistor is connected to the drain of the first transistor. The device is configured to select the first reference voltage such that the output current of the current source varies with changes in a temperature of the current source to maintain the transconductance of the inverter at a same value and prevent changes in respective transition frequencies of both the first transistor and the second transistor.